1. Field of the Invention
The present invention relates to a multibeam exposure device structured so as to be able to measure light quantity data in order to improve exposure quality by adjustment of exposure quantities and shading adjustment which make a light quantity distribution uniform, when carrying out scan-exposure by using a multibeam emitted from a spatial light modulator provided at an exposure head.
2. Brief Description of the Related Art
In recent years, development has advanced of multibeam exposure devices which use spatial light modulators such as digital micromirror devices (DMDs) as pattern generators, and which carry out image exposure on a member-to-be-exposed, by a light beam modulated in accordance with image data.
A DMD is a mirror device in which, for example, a large number of micromirrors, at which the angles of the reflecting surfaces thereof are varied in accordance with control signals, are lined-up in two dimensions on a semiconductor substrate of silicon or the like. The angles of the reflecting surfaces of the micromirrors are varied by electrostatic forces due to electric charges accumulated in respective memory cells.
A multibeam exposure device using a conventional DMD uses an exposure head in which, for example, laser beams emitted from a light source are collimated by a lens system, the respective laser beams are reflected by the plural micromirrors of a DMD disposed substantially at the focal point position of the lens system, and the respective beams are emitted from plural beam exit openings.
Such a multibeam exposure device has been proposed which carries out image exposure at a high resolution by forming an image, by making the spot diameters small, on the recording surface of a photosensitive material (a member-to-be-exposed) by a lens system having an optical element such as a microlens array or the like which collects, at a single lens and for each one pixel, each beam emitted from the beam exit opening of the exposure head (see, for example, Japanese National Publication No. 2002-520840).
In such a multibeam exposure device, the respective micromirrors of the DMD are on/off controlled by an unillustrated control device on the basis of control signals generated in accordance with image data or the like, and the laser beams are modulated (deflected), and the modulated laser beams are irradiated onto the exposure surface (recording surface) and exposure is carried out.
A photosensitive material (a photoresist or the like) is disposed at the recording surface. This multibeam exposure device is structured so as to be able to carry out processing for exposing a detailed pattern on the photosensitive material in a short period of time, by modulating respective DMDs in accordance with image data, while relatively moving, with respect to the photosensitive material, the positions of the beam spots where the laser beams are irradiated and form images on the photosensitive material from plural recording heads.
In this multibeam exposure device, in accordance with the changes over time from before the start of exposure to during the exposure processing, the light quantity distribution of the laser light in the exposure-on state from the DMD set at the exposure head is measured, and it is necessary to carry out adjustment of the exposure quantities and shading adjustment for adjusting the light quantity distribution of the laser light to be uniform.
Thus, the following structure has been conceived of, for example: the driving of the DMD is controlled such that respective one columns of micromirrors along the scanning direction with respect to the photosensitive material are switched to the exposure-on state column-by-column and in order. The light quantities of the laser lights reflected at the DMD are detected by using a two-dimensional light detector such as a photodiode (PD) or a Charge Coupled Device (CCD) or the like, and the light quantity distribution of the DMD with respect to the direction orthogonal to the scanning direction is determined.
However, when the light quantity distribution of the DMD is determined as described above, the determination is affected by so-called stray light which is reflected by the large number of micromirrors of the DMD in off states and which is incident on the two-dimensional light detector. There is therefore the problem that it is difficult to measure accurate light quantity data such as the light quantity distribution or the like.